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A269823 Number of n X 2 0..4 arrays with some element plus some horizontally, diagonally, antidiagonally or vertically adjacent neighbor totaling four exactly once. 1
5, 216, 3096, 39784, 462680, 5145736, 55265336, 580002280, 5978552216, 60784629832, 611189228792, 6090202880680, 60229576820312, 591855697435912, 5784216137341880, 56261693581866856, 544976552619855128 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 10*a(n-1) + 47*a(n-2) - 336*a(n-3) - 1416*a(n-4) - 864*a(n-5) - 144*a(n-6) for n>7.
Empirical g.f.: x*(5 + 166*x + 701*x^2 + 352*x^3 - 1016*x^4 - 480*x^5 + 720*x^6) / (1 - 5*x - 36*x^2 - 12*x^3)^2. - Colin Barker, Jan 29 2019
EXAMPLE
Some solutions for n=4:
..4..2. .2..0. .1..1. .3..3. .1..4. .4..2. .1..1. .3..3. .2..4. .2..3
..1..4. .0..3. .4..2. .2..2. .2..0. .1..1. .2..0. .4..4. .3..0. .0..4
..1..2. .2..0. .3..0. .4..4. .0..0. .4..2. .1..2. .2..1. .3..3. .1..1
..2..0. .4..3. .3..0. .4..4. .1..2. .3..2. .1..4. .0..2. .2..0. .2..1
CROSSREFS
Column 2 of A269829.
Sequence in context: A048433 A270870 A144796 * A206457 A291806 A119657
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 05 2016
STATUS
approved

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Last modified February 22 12:59 EST 2024. Contains 370255 sequences. (Running on oeis4.)